JP3039567B2 - Four-wheel steering system for vehicles - Google Patents

Description

BACKGROUND OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a four-wheel steering system.
ystem: 4 wheel steering device or 4 wheel steering device)
More specifically, turning safety performance (cornering stability) is optimized by optimally adjusting the rear wheel steering angle according to the vehicle speed, front wheel steering angle (steering) angle, and lateral acceleration. The present invention relates to a four-wheel steering system that can be improved.

In particular, the present invention relates to an independent steering system that can independently steer each rear wheel.

(2) Description of Related Art Generally, a normal vehicle steering system includes an operation (handling) mechanism including a steering wheel, a steering (steering) shaft and a column, and a steering gear and a link mounted on a frame. A gear mechanism and a link mechanism including a hit-unarm, a drag link, and a tie rod are provided.

Such a steering system is designed to adjust the steering direction of the front wheels by gear-driving the tie rods left and right according to the rotation direction of a gear attached to one end of a steering shaft. 2. Description of the Related Art In recent years, power steering systems that can improve the safety performance of operation (handling) have become widespread.

However, since these steering systems are designed so that only the front wheels are steered, there is a problem that the vehicle body suddenly leans and becomes unstable while the vehicle turns at high speed. Therefore, in recent years, a four-wheel steering system capable of simultaneously steering the front wheel and the rear wheel has been developed.

An example of this four-wheel steering system is disclosed in US Pat. No. 4,778,023.
Nos. 4,781,262, 4,821,830, 4,888,613 and 5,220,974.

However, many conventional four-wheel steering systems are designed such that multiple rear wheels are adjusted with only one rear wheel actuator.

This can provide stability during a simple cornering, but during a sudden lane change or slalom run, the rapid response of the wheels inside the turn due to the inertia of the four-wheel steering system I can't get it. As a result, oversteering occurs in which the rear end of the vehicle body is pushed to the outside of the turn, and the marginal performance and the stability performance of the vehicle decrease.

SUMMARY OF THE INVENTION The present invention is in an effort to solve the problems described above.

An object of the present invention is to provide a four-wheel steering system capable of improving turning (cornering) safety by optimally adjusting a rear wheel steering angle according to a vehicle speed, a front wheel steering angle, and a lateral (lateral) acceleration. Is to provide.

It is another object of the present invention to provide an independent steering system that can independently steer (steer) each rear wheel.

To achieve the above object, the present invention provides a steering wheel, a front pump and a rear pump driven by an engine that generates hydraulic pressure, a front direction control valve having a port that opens and closes based on a rotation direction of the steering wheel, A front wheel actuator having left and right chambers to which fluid pressure is supplied through a flow path selected by the direction control valve, at least in response to signals transmitted from a vehicle speed sensor, a steering angle sensor, and a steering amount feedback sensor; An electronic control unit for controlling wheel steering; a first solenoid for returning hydraulic pressure generated in the rear pump to a reservoir tank in response to a signal sent from the electronic control unit, or for supplying hydraulic pressure as an operating pressure Valve, from the electronic control unit A second solenoid valve that returns the hydraulic pressure generated in the rear pump to the reservoir tank in response to the transmitted signal or supplies the hydraulic pressure, The first solenoid in response to a signal transmitted from the electronic control unit A first rear direction control valve for changing a flow direction of hydraulic pressure supplied from a valve; a second rear for changing a flow direction of hydraulic pressure supplied from the second solenoid valve in response to a signal sent from the electronic control unit; A direction control valve, a first rear wheel actuator having a left chamber and a right chamber into which the hydraulic pressure supplied from the first rear direction control valve flows, and the hydraulic pressure supplied from the second rear direction control valve flows into the first rear wheel actuator A second rear wheel actuator having a left chamber and a right chamber, the first and the second wheels being connected to each of the rear wheels. A first pivoting member rotatably connected to the vehicle body by a first universal joint, rotatably about a hinge point, one of its free ends being said first rear wheel; Coupled to an actuator, a second pivot member rotatably connected to the vehicle body by a second universal joint, rotatably about a hinge point, wherein one of its free ends is the second pivot member; Connected to a rear wheel actuator, the other of the respective free ends of the first and second pivot members, and two of the free ends of the first and second wheel supports connected to one of the free ends. A first link, one end of which is connected to the other of the free ends of the first and second wheel supports, and the other end of which is connected to the vehicle body via a universal joint; 2, which is connected
The first and second solenoid valves are independently controlled by the electronic control unit; the first and second rear directional control valves are also independently controlled by the electronic control unit; In a traveling state, the electronic control unit drives the first and second solenoid valves, the first and second rear direction control valves, and the first and second rear wheel actuators to drive the steering angle of the rear wheels. To the steering angle according to the steering angle of the steering wheel, in the case of sudden lane change or slalom traveling,
The electronic control unit provides a four-wheel steering system for a vehicle, in which a rear wheel on a turning inside is controlled to a neutral position and a rear wheel on a turning outside is steered.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and
Together with the detailed description, they are provided to illustrate the principles of the present invention.

FIG. 1 is a view showing a steering system according to a preferred embodiment of the present invention.

FIG. 2 is a diagram illustrating a steering system in which a plurality of rear wheels are adjusted to have the same pointing direction as a plurality of front wheels.

FIG. 3 is a drawing illustrating a steering system in which only one rear wheel is adjusted to have the same pointing direction as a plurality of front wheels.

FIG. 4 is a diagram illustrating a steering system that adjusts a plurality of rear wheels so as to be in opposite directions to a plurality of front wheels.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a vehicle steering (steering) system (apparatus) of the present invention, in which front wheels 2, 4 are connected to tie rods 6, 8 respectively by universal joints. As a result, the front wheels 2, 4 are steered (steered or steered) by the movement of the piston rods 12, 14 arranged on both sides of the front wheel actuator 10, respectively.

The front wheel steering (steering) unit 26 includes a front direction control valve 18 for controlling a flow direction of hydraulic pressure according to a rotation direction of the steering wheel 16 and a front pump 24 for generating hydraulic pressure. I have. The left and right ports 28, 30 of the front direction control valve 18 are connected to the left and right chambers 10a, 1
0b, respectively. The outlet of the front pump 24 is connected to the front direction control valve 18.

Left and right ports 28 of the front direction control valve 18,
Numeral 30 is selectively opened (opened) according to the rotation direction of the steering wheel 16 to supply hydraulic pressure to each of the left and right ports of the front wheel actuator 10.

That is, as illustrated in FIG. 1, when the vehicle is in the straight ahead position in the forward direction, the left and right ports 28 and 30 of the front direction control valve 18 are closed, and the bypass port 32 is opened. The generated hydraulic pressure flows into a reservoir (storage) tank 34.

The rear wheel steering (steering) unit 50 includes first and second rear direction control valves 42 and 44 and first and second rear wheel actuators 46 and 48, and receives hydraulic pressure from a rear pump 36 through a passage 52.

The first and second solenoid valves 54 and 56 selectively supply the hydraulic pressure to the rear wheel steering unit 50, or supply the hydraulic pressure to a reservoir tank.
It is connected to the passage 52 so as to return to 34.

The first and second solenoid valves 54 and 56 and the first and second rear direction control valves 42 and 44 are electrically connected to the output terminal of the electronic control unit ECU. Control opening and closing.

The electronic control unit ECU has a steering angle sensor 58 and a vehicle speed sensor 6
0, acceleration sensor 62, front wheel steering amount feedback sensor 6
4, 66, and rear wheel steering amount feedback sensors 68, 7
It has an input to which 0, 72, and 74 are connected to receive signals from each sensor.

When those signals are input to the electronic control unit ECU, the electronic control unit ECU starts the first and second solenoid valves 5.
The steering angles of the rear wheels 38, 40 are adjusted by controlling the fourth, 56 and first and second rear direction control valves 42, 44.

The first rear directional control valve 42 has five ports 76, 78,
A valve casing 86 defining 80, 82, 84 and a valve spool 94 movably disposed within the casing and having three lands 88, 90, 92 formed therein.

The second rear direction control valve 44 has the same structure as the first rear direction control valve 42. That is, the second rear directional control valve 44 includes a valve casing 87 having five ports 77, 79, 81, 83, and 85, and three lands formed therein.
And a valve spool 95 having 89, 91, 93.

Port 7 of each of the first and second rear directional control valves 42 and 44
8, 79 communicate with each other and are connected to the reservoir tank. Ports 82 and 84 are the first rear wheel actuator
It communicates with the left and right chambers 96, 98 of 46. Each of the ports 83, 85 communicates with the left and right chambers 100, 102 of the second rear wheel actuator 48.

Ports 76 and 80 of the first rear directional control valve 42 and ports 77 and 81 of the second rear directional control valve 44 are first and second ports, respectively.
Outlet ports 104, 105 of each of the two solenoid valves 54, 56
And receives hydraulic pressure therefrom.

The first solenoid valve 54 has three ports 104, 108,
There is provided a valve casing 112 having 110 and a valve spool 118 having two lands 114, 116 formed thereon.

The second solenoid valve 56 has three ports 105, 109, 11
1 with a valve casing 113 and 2 formed therein.
And a valve spool 119 having two lands 115 and 117.

The ports 108 and 109 of the first and second solenoid valves 54 and 56 communicate with each other and are connected to the reservoir tank 34. The ports 110 and 111 are connected to the rear pump 36 through the passage 52.
And receives hydraulic pressure therefrom.

First rear wheel actuator 46 and second rear wheel actuator
48 are mounted independently of each other and do not cooperate with each other.

The pistons 120, 122 of each actuator 46, 48 are connected by universal joints to pivot members 128, 130 through piston rods 124, 126, respectively.

The pivot members 128 and 130 are respectively provided at one end and the other end thereof by a universal joint to the vehicle body B.
And rotates clockwise or counterclockwise according to the moving direction of each piston 120, 122.

The pivot members 128 and 130 are connected at their other ends to wheel supports 136 and 138 through first links 132 and 134, respectively. Wheel support 13
6 and 138 are connected to the vehicle body B by universal joints through the second links 140 and 142, respectively.
30 and 40 are rotatably supported.

As described above, in the steering system of the present invention, as shown in FIG. 2, when the steering wheel 16 is turned to the left during traveling, the left port of the front direction control valve 18 is moved.
28 is opened, so that the hydraulic pressure generated by the front pump 24
Supplied to a.

As a result, when the piston of the front wheel actuator 10 moves to the right as shown in FIG. 2, the piston rod 12 is pulled and the piston rod 14 is pushed, so that the front wheels 2, 4 are turned to the left by the respective tie rods 6, 8.

At this time, the steering angle sensor 58, the vehicle speed sensor 60,
Signals detected by the lateral acceleration sensor 62 and the front wheel steering amount feedback sensors 64 and 66 are input to the electronic control unit.

These input signals are changing signals that substantially determine the steering behavior of the rear wheels 38,40.

These signals for controlling the steering of the rear wheels are input to one or both of the first solenoid valve 54 and the second solenoid valve 56.

When a signal is input to one or both of the first and second solenoid valves 54 and 56, as shown in FIG. 2, the valve spools 118 and 119 of the solenoid valves 54 and 56 respectively.
Are positioned in a neutral state.

Accordingly, the hydraulic pressure generated by the rear pump 36 flows along the passage 52 along the ports 11 of the first and second solenoid valves 54 and 56.
0, 111 and out through ports 104, 108 and 105, 109.

At this point, the hydraulic pressure flowing through one of ports 108, 109 returns to reservoir tank 34 and
The hydraulic pressure flowing out through the ports 105 and 105 flows into the ports 76 and 80 of the first rear direction control valve 42 and the ports 77 and 81 of the second rear direction control valve 44.

At this point, the first and second rear directional control valves 42,
Since the 44 valve spools 94 and 95 move to the right in the drawing, only the hydraulic pressure flowing into the ports 80 and 81 is
4 and 85, the right chamber 98 of the first rear wheel actuator 46 and the right chamber 102 of the second rear wheel actuator 48
Flows into.

Accordingly, the pistons 120, 122 of the first and second rear wheel actuators 46, 48 move to the left, respectively, whereby the piston rods 124, 126 move to the left.

With this operation, the pivot members 128 and 130 connected to the vehicle body B by the universal joint rotate counterclockwise around each hinge point H. As a result, the first link 13 connected to the pivot members 128, 130
2, 134 move in opposite directions to the piston rods 124, 126, respectively, thereby steering the wheel supports 136, 138 as shown in FIG.

In this state, the rear wheels 38, 40 are adjusted to have the same pointing direction as the front wheels 2, 4, so that the diameter of the path created by the front wheels rather than when the vehicle is steered by only the steerable front wheels And the turn safety performance increases.

On the other hand, when the vehicle suddenly changes lanes or runs in a slalom, the steering inertia must be reduced to improve the response performance in response to the steering. Thus, to reduce steering inertia, the steering system of the present invention is designed such that the rear wheels outside the turn are steered and the rear wheels inside the turn are in a neutral position.

This is made possible by independently controlling the rear wheels. Therefore, in the present invention, when the vehicle turns to the left, only the right rear wheel 40 is operated as shown in FIG.
When the vehicle turns further to the right, the left rear wheel 38 can be steered immediately.

Such selective control of the rear wheels is achieved by a first rear control valve.
This is achieved by controlling the second rear direction control valve 44 to a state as shown in FIG.

FIG. 4 shows a state in which the traveling directions of the rear wheels 38 and 40 are adjusted to be opposite to the pointing directions generated by the front wheels 2 and 4. The front wheels 2, 4 turn right while the rear wheels 38, 40 turn left.

This adjustment can further reduce the turning radius of the vehicle as compared to when the rear wheels are adjusted in the same pointing direction as the front wheels. The selective steering of the rear wheels is based on signals input from the steering amount feedback sensors 64 and 66.

As described above, in the four-wheel steering system of the present invention, the rear wheels are independently controlled by the two solenoid valves according to the turning angle of the steered wheels, so that the rear wheels are transmitted by the electronic control unit ECU. It is adjusted optimally according to the signal to be performed.

Further, when the vehicle is turning at a high speed, the rear wheels on the outside of the turn are steered by the electronic control unit in a steering direction corresponding to the steering wheel 16, and the rear wheels on the inside of the turn are controlled by the electronic control unit according to the steering wheel 16. The steering is performed in a direction opposite to the steering direction.

When the vehicle is turning at low speed, as illustrated in FIG. 4, the steering direction of the rear wheels is adjusted opposite to the direction of travel produced by the front wheels so that the vehicle can steer even on narrow roads. I do.

While the preferred embodiment of the present invention has been described in detail, various modifications and / or modifications of the basic inventive concepts taught herein that can be devised by those skilled in the art are set forth in the accompanying claims. Included in the scope of technical thought is:
You will understand clearly.

Continuation of the front page (56) References JP-A-5-155349 (JP, A) JP-A-53-40930 (JP, A) JP-A-60-92981 (JP, A) JP-A-63-192670 (JP, A) , A) Fully open 1987-31576 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B62D 7/14 B62D 6/00

Claims (4)

(57) [Claims] 1. A steering wheel, a front pump and a rear pump driven by an engine that generates hydraulic pressure, a front directional control valve having a port that opens and closes based on a rotation direction of the steering wheel, selected by the front directional control valve Front wheel actuator having a left chamber and a right chamber to which the hydraulic pressure is supplied through a flow path, and controls the steering of the rear wheels according to signals transmitted from at least a vehicle speed sensor, a steering angle sensor, and a steering amount feedback sensor. An electronic control unit that returns a hydraulic pressure generated in the rear pump to a reservoir tank in response to a signal sent from the electronic control unit, or supplies a hydraulic pressure as an operating pressure; Depending on the signal sent from A second solenoid valve for returning the hydraulic pressure generated in the rear pump to the reservoir tank or supplying the hydraulic pressure; a hydraulic pressure supplied from the first solenoid valve in response to a signal sent from the electronic control unit A first rear direction control valve for changing a flow direction of the fluid; a second rear direction control valve for changing a flow direction of a hydraulic pressure supplied from the second solenoid valve in response to a signal sent from the electronic control unit; A first rear wheel actuator having a left chamber and a right chamber into which a hydraulic pressure supplied from a rear direction control valve flows; and a left and right chamber into which a hydraulic pressure supplied from the second rear direction control valve flows. A second rear wheel actuator having first and second wheel supports coupled to each of the rear wheels; A first pivoting member rotatably connected to the vehicle body by a first universal joint, rotatably about a j-point, one of its free ends connected to the first rear wheel actuator. A second pivoting member rotatably connected to the vehicle body by a second universal joint, rotatably about a hinge point, one of its free ends connected to the second rear wheel actuator. The other of the respective free ends of the first and second pivot members and two first links connected to one of the free ends of the first and second wheel supports, respectively. Are connected to the other of the free ends of the first and second wheel supports, and the other ends of the two are connected to the vehicle body via a universal joint. The first and second solenoid valves are independently controlled by the electronic control unit, and the first and second rear direction control valves are also independently controlled by the electronic control unit. , The electronic control unit includes the first and second solenoid valves, the first and second solenoid valves.
Driving a rear direction control valve and the first and second rear wheel actuators to set the steering angle of the rear wheel to a steering angle corresponding to the steering angle of the steering wheel; In the case of (1), the electronic control unit controls the rear wheel on the inside of the turn to the neutral position and steers the rear wheel on the outside of the turn. A first port for receiving a hydraulic pressure from the rear pump; a second port for returning a hydraulic pressure supplied through the first port to the reservoir tank; Third to supply directional control valve
A valve casing having a port, wherein the second solenoid valve has a first port for receiving hydraulic pressure from the rear pump, a second port for returning hydraulic pressure supplied through the first port to the reservoir tank, The four-wheel steering system for a vehicle according to claim 1, further comprising a valve casing having a third port for supplying pressure to the second rear direction control valve. 3. The first rear directional control valve is provided with the first rear direction control valve.
A valve casing having first and second ports for receiving hydraulic pressure from a solenoid valve, and a third port for supplying hydraulic pressure to a left chamber and a right chamber of the first rear wheel actuator; The valve has first and second ports for receiving hydraulic pressure from the second solenoid valve,
The four-wheel steering system for a vehicle according to claim 1 or 2, further comprising a valve casing having a third port for supplying a left chamber and a right chamber of the rear wheel actuator. 4. A front wheel steering unit including a front direction control valve having a port that opens and closes in accordance with the rotation direction of the steering wheel, a front wheel actuator that pushes or pulls a tie rod connected to the front wheel, a vehicle speed sensor, and a steering angle. A sensor, an electronic control unit that controls the steering of the rear wheel according to a signal transmitted from the steering amount feedback sensor, first and second solenoid valves that are independently controlled by the electronic control unit, and independent by the electronic control unit. Controlled first and second rear directional control valves, first or second pulling or pushing the front and rear wheels selectively or simultaneously
2 rear wheel actuators, 1st and 2nd wheel supports respectively connected to the rear wheels, 1st and 2nd wheels respectively connected to the vehicle body by universal joints so as to be rotatable around hinge points. A pivot member having one of its free ends coupled to the first and second rear wheel actuators; the other of the respective free ends of the first and second pivot members; Two first links connected to one of the free ends of the first and second wheel supports, one end of each being connected to the other of the free ends of the first and second wheel supports, respectively And a rear wheel steering unit including two second links connected to the vehicle body via a universal joint. The control unit includes the first and second solenoid valves, the first and second solenoid valves.
Driving a rear direction control valve and the first and second rear wheel actuators to set the steering angle of the rear wheel to a steering angle corresponding to the steering angle of the steering wheel; In the case of (1), the electronic control unit controls the rear wheel on the inside of the turn to the neutral position and steers the rear wheel on the outside of the turn.